Bearings which comprise a core and a sheath surrounding said core are already known from the prior art. The core here by way of at least one elastomer or a plurality of elastomers is supported in relation to the sheath.
One functional chamber or a plurality thereof in which operating fluids are received is/are disposed between the core and the sheath. Often, the functional chambers at their axial ends are delimited by the elastomers which bond the core to the sheath.
Such bearings are referred to as hydraulic bearings and usually have two functional chambers which are closed off and interconnected, and in which in each case one operating fluid is received.
As soon as a hydraulic bearing is cooled, various coefficients of expansion of the core, of the sheath, and of the elastomers and of the operating fluid begin to display their effect.
The operating fluid in the functional chambers usually displays a substantially higher coefficient of expansion than the surrounding, substantially hard delimiting materials. These delimiting materials are usually made from metal or elastomers.
On account of cooling, a cavity or a void, respectively, which has to be equalized is created in the functional chambers. The formation of this void leads to a pressure drop in the entire bearing system.
In as far as residual air is contained post filling in the functional chambers, said residual air expands on account of the drop in pressure and provides a corresponding equalization of volume.
The more residual air received in the functional chambers, the lower the pressure drop in the bearing. However, an air bubble which is created is substantially always the same size as the loss of volume of the operating fluid.
Against this background it should be noted that the pressure in the functional chambers drops under the influence of the vapor pressure of the operating fluid, if no residual air is contained in the functional chambers. The operating fluid evaporates and fills the cavity which has been created or the void which has been created, respectively, in which case the system pressure corresponds to the vapor pressure of the operating fluid.
The behavior described above becomes more complex if very different amounts of air have been received in the two functional chambers. Asymmetrical stiffness profiles result on account thereof.
In any case, when the core deflects in relation to the sheath, first a void which has been created has to be equalized independently of the frequency or speed, respectively, of the deflection, prior to any significant increase in pressure taking place in the functional chamber. Up to this point, the bearing only has the modest bearing-spring stiffness; the higher exalted spring stiffness only begins to take effect thereafter.